Method for processing at least one carbon fiber, method for fabricating a carbon copper composite, and carbon copper composite

ABSTRACT

A method for processing at least one carbon fiber according to an embodiment may include: electroplating a first metal layer over at least one carbon fiber, wherein the first metal layer includes a metal which can form a common phase with carbon, electroplating a second metal layer over the first metal layer, wherein the second metal layer includes a metal which can form a common phase with the metal of the first metal layer, and annealing the at least one carbon fiber, the first metal layer, and the second metal layer so that the metal of the first metal layer forms a common phase with the carbon of the at least one carbon fiber at an interface between the first metal layer and the at least one carbon fiber and the metal of the first metal layer forms a common phase with the metal of the second metal layer at an interface between the first metal layer and the second metal layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/591,265, filed Aug. 22, 2012, the contents of which are incorporatedby reference.

BACKGROUND

Various embodiments relate generally to a method for processing at leastone carbon fiber, a method for fabricating a carbon copper composite,and to a carbon copper composite.

Electronic devices, e.g. power electronic devices, generally produceheat during operation. It may be desirable to provide suitable heatsinks to dissipate the heat produced by the electronic devices.

SUMMARY

A method for processing at least one carbon fiber in accordance with anembodiment may include: electroplating a metal layer over at least onecarbon fiber, wherein the metal layer contains or consists of a metal,which forms a common phase with carbon and a common phase with copper;annealing the at least one carbon fiber and the metal layer.

A method for processing at least one carbon fiber in accordance withanother embodiment may include: electroplating a first metal layer overat least one carbon fiber, wherein the first metal layer contains orconsists of a metal, which forms a common phase with carbon and a commonphase with nickel; electroplating a second metal layer over the firstmetal layer, wherein the second metal layer contains or consists ofnickel; annealing the at least one carbon fiber, the first metal layerand the second metal layer.

A method for fabricating a carbon copper composite in accordance withanother embodiment may include: providing a plurality of carbon fibers;electroplating a metal layer over the plurality of carbon fibers,wherein the metal layer contains or consists of a metal, which forms acommon phase with carbon and a common phase with copper; annealing theplurality of carbon fibers and the metal layer; electroplating a copperlayer over the metal layer.

A method for fabricating a carbon copper composite in accordance withanother embodiment may include: providing a plurality of carbon fibers;electroplating a first metal layer over the plurality of carbon fibers,wherein the first metal layer contains or consists of a metal, whichforms a common phase with carbon and a common phase with nickel;electroplating a second metal layer over the first metal layer, whereinthe second metal layer contains or consists of nickel; annealing theplurality of carbon fibers, the first metal layer and the second metallayer; electroplating a copper layer over the second metal layer.

A method for fabricating a carbon copper composite in accordance withanother embodiment may include: providing a carbon fiber fabric;electroplating a first metal layer onto the fabric, the first metallayer containing or consisting of chromium or manganese; electroplatinga second metal layer onto the first metal layer, the second metal layercontaining or consisting of nickel; annealing the fabric, the firstmetal layer and the second metal layer; electroplating a copper layeronto the second metal layer.

A carbon copper composite in accordance with another embodiment mayinclude: a plurality of carbon fibers; a metal layer disposed over thecarbon fibers, the metal layer containing or consisting of a metal thatforms a common phase with carbon and a common phase with copper; acopper layer disposed over the metal layer.

A carbon copper composite in accordance with another embodiment mayinclude: a plurality of carbon fibers; a first metal layer disposed overthe carbon fibers, wherein the first metal layer contains or consists ofa first metal, which forms a common phase with carbon and a common phasewith nickel; a second metal layer disposed over the first metal layer,wherein the second metal layer contains or consists of nickel; a copperlayer disposed over the second metal layer.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilyto scale, emphasis instead generally being placed upon illustrating theprinciples of various embodiments. In the following description, variousembodiments are described with reference to the following drawings, inwhich:

FIG. 1A shows a method for processing at least one carbon fiber inaccordance with an embodiment;

FIG. 1B shows a method for processing at least one carbon fiber inaccordance with another embodiment;

FIG. 2A shows a method for fabricating a carbon copper composite inaccordance with another embodiment;

FIG. 2B shows a method for fabricating a carbon copper composite inaccordance with another embodiment;

FIG. 3 shows a method for fabricating a carbon copper composite inaccordance with another embodiment;

FIG. 4 shows a method for fabricating a carbon copper composite inaccordance with another embodiment;

FIG. 5 shows a method for fabricating a carbon copper composite inaccordance with another embodiment;

FIG. 6 shows a method for fabricating a carbon copper composite inaccordance with another embodiment;

FIG. 7A to FIG. 10B illustrate various process stages in a method forfabricating a carbon copper composite in accordance with anotherembodiment;

FIG. 11 to FIG. 14 show phase diagrams for illustrating aspects ofvarious embodiments;

FIG. 15A and FIG. 15B show electron microcraphs for illustrating aspectsof various embodiments.

DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific details and embodiments inwhich the invention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention. Other embodiments may be utilized and structural, logical,and electrical changes may be made without departing from the scope ofthe invention. The various embodiments are not necessarily mutuallyexclusive, as some embodiments can be combined with one or more otherembodiments to form new embodiments.

Electronic devices, e.g. power electronic devices, generally produceheat during operation. It may be desirable to provide suitable heatsinks to dissipate the heat produced by the electronic devices. A heatsink for a power electronic device or component (e.g. a high powermodule such as an IGBT (insulated gate bipolar transistor) module) may,for example, mean the intermediate storage of a pulse-like heat loss ofa power switch, which may be caused, for example, by ashort-circuit-like current upon switch-on of a light bulb during thetime the filament of the bulb is cold.

A heat sink may preferably have one or more (e.g. all) of the followingproperties: an electrical conductivity substantially higher than that ofsilicon, a thermal conductivity at least equal to that of silicon, aspecific heat substantially higher than that of silicon.

Pure copper meets the aforementioned requirements very well. However,the difference between the coefficient of thermal expansion (CTE) ofcopper (CTE_(cu)≈16.5*10⁻⁶K⁻¹) and that of silicon(CTE_(Si)≈2.6*10⁻⁶K⁻¹) is rather large so that thermal stress generatedin a thin silicon chip and at the silicon-copper interface between thechip and the heat sink due to the CTE difference may be difficult tocontrol.

A composite of carbon fibers and copper (in the following referred to asCCu) has been proposed as alternative heat sink material. Though thethermal conductivity of CCu is not significantly higher than that ofsilicon, CCu yields a CTE of about 4*10⁻⁶ K⁻¹ to 6*10⁻⁶ K¹, which ismuch closer to the CTE of silicon (2.6*10⁻⁶ K⁻¹) compared to the CTE ofpure copper (16.5*10⁻⁶ K⁻¹). Therefore, the use of CCu as heat sinkmaterial may greatly reduce thermal stress and chip bending.Furthermore, the other above-mentioned requirements for a heat sink maybe very well fulfilled by CCu.

A conventional method for fabricating CCu is based on electroplatingshort carbon fibers with copper, and subsequently sintering the fibersin hot presses at temperatures of around 1000° C. and pressures ofseveral dozen bars. It is assumed that sintering is necessary but notyet sufficient for good thermal coupling between the copper and thecarbon fibers. Therefore, additives are used in addition to achievebetter adhesion of the copper and prevent sliding of the copper on thecarbon fibers during thermal cycling stress. A shift of the phaseboundary on atomic scale would have a negative effect on both thethermal coupling and the average CTE.

One drawback of the aforementioned conventional method may be seen inthat the carbon fiber copper parts may be prefabricated as sinteredparts only. Cold fabrication of the composite directly at a wafer maynot be possible using this method.

Another drawback of the aforementioned conventional method may be seenin that the additives, which are added to the copper electrolyte duringthe pre-copper plating of the short carbon fibers to achieve betteradhesion of the copper on the fibers, possibly do not wet the surface ofthe carbon fibers entirely. Furthermore, the additives may have anegative effect on the properties of the copper.

One aspect of various embodiments described herein may be seen in thatone or more of the drawbacks of the above-described conventional methodmay be obviated or substantially reduced.

FIG. 1A shows a method 100 for processing at least one carbon fiber inaccordance with an embodiment.

In 102, a metal layer may be electroplated (in other words, deposited bymeans of electroplating or, in still other words, electrolyticallydeposited, also referred to as galvanic or electrolytic deposition) overat least one carbon fiber (for example a plurality of carbon fibers,e.g. a layer having a plurality of carbon fibers, e.g. a fabric having aplurality of carbon fibers). In other words, the at least one carbonfiber may be coated with a metal.

The term “over” as used herein in expressions such as “electroplatedover”, “deposited over”, “disposed over”, “formed over”, “arrangedover”, etc., may be understood to include both the case where a firstelement (structure, layer, etc.) is disposed or formed on a secondelement (structure, layer, etc.) with direct physical and/or electricalcontact, and the case where one or more elements (structures, layers,etc.) may be disposed or formed between the first element (structure,layer, etc.) and the second element (structure, layer, etc.).

In accordance with an embodiment, the at least one carbon fiber may havea length in the millimeter range, for example a few millimeters. Other,e.g. higher, values may be possible as well in accordance with otherembodiments. In accordance with one or more embodiments, the at leastone carbon fiber may include graphite.

In accordance with another embodiment, the at least one carbon fiber mayhave a diameter in the range from about 1 μm to about 50 μm. Othervalues may be possible as well in accordance with other embodiments.

The metal layer may contain or consist of a metal, which forms a commonphase with carbon and a common phase with copper.

The term “phase” as used herein may be understood to refer to a solidstate phase. The term “common phase” as used herein may be understood torefer to a stoichiometrically determined solid state phase of a binarysystem (in other words, a system of two components), as may be indicatedin a corresponding phase diagram of the binary system. For example, theterm “common phase of component X and component Y” may be understood torefer to any stoichiometrically determined solid state phase in thephase diagram corresponding to the binary system X-Y. For example, theterm “common phase of carbon (C) and chromium (Cr)” may be understood torefer to any stoichiometrically determined solid state phase in thephase diagram corresponding to the binary system C—Cr (see e.g. phasediagram 1100 in FIG. 11).

In accordance with an embodiment, the metal may be chromium (Cr) ormanganese (Mn).

In accordance with another embodiment, electroplating the metal layermay include or may be effected by pulsed electroplating (herein alsoreferred to as pulse electroplating, pulse galvanic, or galvanic pulsedeposition). The term “pulsed electroplating” as used herein may beunderstood to refer to an electroplating (electrolytic deposition)technique, in which a plating current may be supplied in one or morepulses of predeterminable duration and/or height.

In accordance with another embodiment, a pulse frequency used in thepulsed electroplating may be in the range from about 10 kHz to about 1MHz. Other values may be possible as well in accordance with otherembodiments.

In accordance with another embodiment, a pulse height of pulses used inthe pulsed electroplating may be in the range from about 4 V to about 12V. Other values may be possible as well in accordance with otherembodiments.

In accordance with other embodiments, electroplating the metal layer maybe effected by means of other suitable electroplating techniques.

The metal layer may at least partially (e.g. fully) coat the at leastone carbon fiber or the plurality of carbon fibers.

In accordance with another embodiment, the metal layer be deposited suchthat it has a layer thickness that is smaller than the diameter of theat least one carbon fiber, for example substantially smaller than thediameter of the at least one carbon fiber, for example a layer thicknessequal to or less than about 25% of the carbon fiber diameter, forexample a layer thickness equal to or less than about 15% of the carbonfiber diameter, for example a layer thickness equal to or less thanabout 10% of the carbon fiber diameter, for example a layer thicknessequal to or less than about 5% of the carbon fiber diameter, for examplea layer thickness equal to or less than about 1% of the carbon fiberdiameter, for example a layer thickness in the range from about 10 nm toabout 500 nm. Other values may be possible as well in accordance withother embodiments. The minimal layer thickness may, for example,correspond to the size of crystallization seeds of the metal layer.

In 104, the at least one carbon fiber and the metal layer may beannealed (in other words, heated or tempered). The at least one carbonfiber and the metal layer may be annealed simultaneously, for example ina single processing step.

In accordance with another embodiment, an annealing temperature may bein the range from about 400° C. to about 1000° C. Other values may bepossible as well in accordance with other embodiments.

In accordance with another embodiment, an annealing time may be in therange from about 1 h to about 10 h. Other values may be possible as wellin accordance with other embodiments.

Annealing the at least one carbon fiber and the metal layer may serve toform a common phase of carbon and the metal of the metal layer, forexample at an interface between the at least one carbon fiber and themetal layer.

In accordance with another embodiment, a copper layer may beelectroplated over the metal layer, as shown in 106. Electroplating thecopper layer may be carried out after annealing the at least one carbonfiber and the metal layer. Electroplating the copper layer may beeffected using any suitable electroplating technique, which are known assuch in the art.

The metal layer may serve as adhesion layer to enable or improveadhesion of the copper layer, as will be described in more detailfurther below.

In accordance with another embodiment, the copper layer may be annealedafter depositing the copper layer, for example to a temperature in therange from about 110° C. to about 150° C. Annealing may, for example,serve to remove (e.g. vaporize) possible electrolyte residues.

FIG. 1B shows a method 150 for processing at least one carbon fiber inaccordance with another embodiment.

In 152, a first metal layer may be electroplated (in other words,deposited by means of electroplating, also referred to as galvanicdeposition or electrolytic deposition) over at least one carbon fiber(for example a plurality of carbon fibers, e.g. a layer having aplurality of carbon fibers, e.g. a fabric having a plurality of carbonfibers). In other words, the at least one carbon fiber may be coatedwith a metal.

In accordance with an embodiment, the at least one carbon fiber may havea length in the millimeter range, for example a few millimeters. Other,e.g. higher, values may be possible as well in accordance with otherembodiments.

In accordance with another embodiment, the at least one carbon fiber mayhave a diameter in the range from about 1 μm to about 50 μm. Othervalues may be possible as well in accordance with other embodiments.

The first metal layer may contain or consist of a metal, which forms acommon phase with carbon and a common phase with nickel. In other words,the metal and carbon may form at least one common phase, and nickel andthe metal may form at least one common phase. The metal of the firstmetal layer may be different from nickel.

The first metal layer may at least partially (e.g. fully) coat the atleast one carbon fiber or the plurality of carbon fibers.

In 154, a second metal layer may be electroplated over the first metallayer, wherein the second metal layer may contain or consist of nickel.The second metal layer may, for example, be a nickel layer.

Illustratively, the first metal layer and the second metal layer may beconfigured such that the metal of the first metal layer and carbon mayform a common phase, and the metal of the first metal layer and themetal of the second metal layer may form a common phase.

In accordance with an embodiment, the metal of the first metal layer maybe chromium (Cr) or manganese (Mn).

In accordance with another embodiment, electroplating the first metallayer and/or electroplating the second metal layer may include or may beeffected by pulsed electroplating (herein also referred to as pulseelectroplating or galvanic pulse deposition).

In accordance with another embodiment, a pulse frequency of pulses usedin the pulsed electroplating may be in the range from about 10 kHz toabout 1 MHz. Other values may be possible as well in accordance withother embodiments.

In accordance with another embodiment, a pulse height of pulses in thepulsed electroplating may be in the range from about 4 V to about 12 V.Other values may be possible as well in accordance with otherembodiments.

In accordance with other embodiments, electroplating the first metallayer and/or electroplating the second metal layer may be effected bymeans of other suitable electroplating techniques.

In accordance with another embodiment, the first metal layer and/or thesecond metal layer may be deposited such that they have a layerthickness that is smaller than the diameter of the carbon fibers, forexample substantially smaller than the diameter of the carbon fibers,for example a layer thickness equal to or less than about 25% of thecarbon fiber diameter, for example a layer thickness equal to or lessthan about 15% of the carbon fiber diameter, for example a layerthickness equal to or less than about 10% of the carbon fiber diameter,for example a layer thickness equal to or less than about 5% of thecarbon fiber diameter, for example a layer thickness equal to or lessthan about 1% of the carbon fiber diameter, for example a layerthickness in the range from about 10 nm to about 500 nm. Other valuesmay be possible as well in accordance with other embodiments. Theminimal layer thickness may, for example, correspond to the size ofcrystallization seeds of the first and/or second metal layer.

In accordance with another embodiment, the first metal layer and thesecond metal layer may have the same or substantially the same layerthickness.

In 156, the at least one carbon fiber, the first metal layer and thesecond metal layer may be annealed.

In accordance with an embodient, the at least one carbon fiber, thefirst metal layer and the second metal layer may be annealedsimultaneously, for example in a single processing step.

In accordance with another embodiment, annealing the at least one carbonfiber and the first metal layer may be carried out before electroplatingthe second metal layer.

In accordance with another embodiment, an annealing temperature may bein the range from about 400° C. to about 1000° C. Other values may bepossible as well in accordance with other embodiments.

In accordance with another embodiment, an annealing time may be in therange from about 1 h to about 10 h. Other values may be possible as wellin accordance with other embodiments.

Annealing the at least one carbon fiber, the first metal layer and thesecond metal layer may serve to form a common phase of carbon and themetal of the first metal layer, for example at an interface between theat least one carbon fiber and the first metal layer, and a common phaseof the metal of the first metal layer and the metal of the second metallayer, for example at an interface between the first metal layer and thesecond metal layer.

In accordance with another embodiment, a copper layer may beelectroplated over the second metal layer, as shown in 158.Electroplating the copper layer may be carried out after annealing theat least one carbon fiber, the first metal layer and the second metallayer. Electroplating the copper layer may be effected using anysuitable electroplating technique, which are known as such in the art.

The first metal layer and the second metal layer may serve as adhesionlayers to enable or improve adhesion of the copper layer, as will bedescribed in more detail further below.

FIG. 2A shows a method 200 for fabricating a carbon copper composite inaccordance with another embodiment.

In 202, a plurality of carbon fibers (e.g. a layer having a plurality ofcarbon fibers) may be provided. The number of carbon fibers may bearbitrary, in general.

In accordance with an embodiment, the plurality of carbon fibers may beconfigured as a fabric. In other words, the plurality of carbon fibersmay be arranged to form a fabric, also referred to as carbon fiberfabric herein. In accordance with one or more embodiments, one or more(e.g. all) of the carbon fibers may include graphite.

In accordance with another embodiment, at least one (for example aplurality, e.g. all) of the carbon fibers may have a length in themillimeter range, for example a few millimeters. Other, e.g. higher,values may be possible as well in accordance with other embodiments.

In accordance with another embodiment, at least one (for example aplurality, e.g. all) of the carbon fibers may have a diameter in therange from about 1 μm to about 50 nm. Other values may be possible aswell in accordance with other embodiments.

In 204, a metal layer may be electroplated (in other words, deposited bymeans of electroplating) over the plurality of carbon fibers.

The metal layer may contain or consist of a metal that forms a commonphase with carbon and a common phase with copper.

In accordance with an embodiment, the metal may be chromium (Cr) ormanganese (Mn).

In accordance with another embodiment, electroplating the metal layermay include or may be effected by pulsed electroplating (herein alsoreferred to as pulse electroplating or galvanic pulse deposition).

In accordance with another embodiment, a pulse frequency of pulses usedin the pulsed electroplating may be in the range from about 10 kHz toabout 1 MHz. Other values may be possible as well in accordance withother embodiments.

In accordance with another embodiment, a pulse height of pulses in thepulsed electroplating may be in the range from about 4 V to about 12 V.Other values may be possible as well in accordance with otherembodiments.

In accordance with other embodiments, electroplating the metal layer maybe effected by means of other suitable electroplating techniques.

The metal layer may at least partially (e.g. fully) coat at least one(for example a plurality, e.g. all) of the carbon fibers.

In accordance with another embodiment, the metal layer may be depositedsuch that it has a layer thickness that is smaller than the diameter ofthe carbon fibers, for example substantially smaller than the diameterof the carbon fibers, for example a layer thickness equal to or lessthan about 25% of the carbon fiber diameter, for example a layerthickness equal to or less than about 15% of the carbon fiber diameter,for example a layer thickness equal to or less than about 10% of thecarbon fiber diameter, for example a layer thickness equal to or lessthan about 5% of the carbon fiber diameter, for example a layerthickness equal to or less than about 1% of the carbon fiber diameter,for example a layer thickness in the range from about 10 nm to about 500nm. Other values may be possible as well in accordance with otherembodiments. The minimal layer thickness may, for example, correspond tothe size of crystallization seeds of the metal layer.

In 206, the plurality of carbon fibers and the metal layer may beannealed.

In accordance with an embodiment, an annealing temperature may be in therange from about 400° C. to about 1000° C. Other values may be possibleas well in accordance with other embodiments.

In accordance with another embodiment, an annealing time may be in therange from about 1 h to about 10 h. Other values may be possible as wellin accordance with other embodiments.

The plurality of carbon fibers and the metal layer may be annealedsimultaneously, for example in a single processing step.

Annealing the plurality of carbon fibers and the metal layer may serveto form a common phase of the carbon of the carbon fibers and the metalof the metal layer, for example at interfaces between the carbon fibersand the metal layer.

In 208, a copper layer may be electroplated over the metal layer.

Electroplating the copper layer may be carried out after annealing theplurality of carbon fibers and the metal layer.

Electroplating the copper layer may be effected using any suitableelectroplating technique, which are known as such in the art.

The metal layer may serve as adhesion layer to enable or improveadhesion of the copper layer, as will be described in more detailfurther below.

FIG. 2B shows a method 250 for fabricating a carbon copper composite inaccordance with another embodiment.

In 252, a plurality of carbon fibers (e.g. a layer having a plurality ofcarbon fibers) may be provided. The number of carbon fibers may bearbitrary, in general.

In accordance with an embodiment, the plurality of carbon fibers may beconfigured as a fabric. In other words, the plurality of carbon fibersmay be arranged to form a fabric, also referred to as carbon fiberfabric herein.

In accordance with another embodiment, at least one (for example aplurality, e.g. all) of the carbon fibers may have a length in themillimeter range, for example a few millimeters. Other, e.g. higher,values may be possible as well in accordance with other embodiments.

In accordance with another embodiment, at least one (for example aplurality, e.g. all) of the carbon fibers may have a diameter in therange from 1 nm to about 50 nm. Other values may be possible as well inaccordance with other embodiments.

In 254, a first metal layer may be electroplated over the plurality ofcarbon fibers.

The first metal layer may contain or consist of a metal, which forms acommon phase with carbon and a common phase with nickel. In other words,the metal and carbon may form at least one common phase, and nickel andthe metal may form at least one common phase. The metal of the firstmetal layer may be different from nickel.

The first metal layer may at least partially (e.g. fully) coat the atleast one carbon fiber or the plurality of carbon fibers.

In 256, a second metal layer may be electroplated over the first metallayer, wherein the second metal layer may contain or consist of nickel.

Illustratively, the first metal layer and the second metal layer may beconfigured such that the metal of the first metal layer and carbon mayform a common phase, and the metal of the first metal layer and nickelmay form a common phase, as described above.

In accordance with an embodiment, the metal of the first metal layer maybe chromium (Cr) or manganese (Mn).

In accordance with another embodiment, electroplating the first metallayer and/or electroplating the second metal layer may include or may beeffected by pulsed electroplating (herein also referred to as pulseelectroplating or galvanic pulse deposition).

In accordance with another embodiment, a pulse frequency of pulses usedin the pulsed electroplating may be in the range from about 10 kHz toabout 1 MHz. Other values may be possible as well in accordance withother embodiments.

In accordance with another embodiment, a pulse height of pulses used inthe pulsed electroplating may be in the range from about 4 V to about 12V. Other values may be possible as well in accordance with otherembodiments.

In accordance with other embodiments, electroplating the first metallayer and/or electroplating the second metal layer may be effected bymeans of other suitable electroplating techniques.

In accordance with another embodiment, the first metal layer and/or thesecond metal layer may be deposited such that they have a layerthickness that is smaller than the diameter of the carbon fibers, forexample substantially smaller than the diameter of the carbon fibers,for example a layer thickness equal to or less than about 25% of thecarbon fiber diameter, for example a layer thickness equal to or lessthan about 15% of the carbon fiber diameter, for example a layerthickness equal to or less than about 10% of the carbon fiber diameter,for example a layer thickness equal to or less than about 5% of thecarbon fiber diameter, for example a layer thickness equal to or lessthan about 1% of the carbon fiber diameter, for example a layerthickness in the range from about 10 nm to about 500 nm. Other valuesmay be possible as well in accordance with other embodiments. Theminimal layer thickness may, for example, correspond to the size ofcrystallization seeds of the first and/or second metal layer.

In accordance with another embodiment, the first metal layer and thesecond metal layer may have the same or substantially the same layerthickness.

In 258, the plurality of carbon fibers, the first metal layer, and thesecond metal layer may be annealed.

In accordance with an embodiment, an annealing temperature may be in therange from about 400° C. to about 1000° C. Other values may be possibleas well in accordance with other embodiments.

In accordance with another embodiment, an annealing time may be in therange from about 1 h to about 10 h. Other values may be possible as wellin accordance with other embodiments.

In accordance with another embodiment, the plurality of carbon fibers,the first metal layer and the second metal layer may be annealedsimultaneously, for example in a single processing step.

Annealing the plurality of carbon fibers, the first metal layer and thesecond metal layer may serve to form a common phase of carbon and themetal of the first metal layer, for example at interfaces between thecarbon fibers and the first metal layer, and a common phase of the metalof the first metal layer and the metal of the second metal layer, forexample at interfaces between the first metal layer and the second metallayer.

In accordance with another embodiment, annealing the plurality of carbonfibers and the first metal layer may be carried out beforeelectroplating the second metal layer.

In 260, a copper layer may be electroplated over the second metal layer.Electroplating the copper layer may be carried out after annealing theplurality of carbon fibers, the first metal layer and the second metallayer. Electroplating the copper layer may be effected using anysuitable electroplating technique, which are known as such in the art.

In accordance with another embodiment, a surface of the second metallayer (e.g. a surface that faces away from the first metal layer) may beactivated before electroplating the copper layer over the second metallayer. Activating the surface of the second metal layer may, forexample, include or be achieved by bringing the surface into contactwith an acid such as hydrochloric acid, e.g. concentrated hydrochloricacid, or other suitable acids, for example for a short time interval(e.g. for about 10 s to about 20 s). In accordance with anotherembodiment, the surface of the second metal layer may be cleaned afteractivating the surface. Cleaning the surface may, for example, includeor be achieved by purging. By means of activating and/or cleaning, anoxide layer (which may have been formed on the surface of the secondmetal layer during the annealing) may, for example, be removed.

In accordance with another embodiment, voids possibly remaining betweenthe plurality of carbon fibers after electroplating the copper layer maybe filled or joined with copper, for example galvanically or by means ofhot pressing.

FIG. 3 shows a method 300 for fabricating a carbon copper composite inaccordance with another embodiment.

In 302, a carbon fiber fabric may be provided. The fabric may have aplurality of carbon fibers. The carbon fibers may, for example, beconfigured in accordance with one or more embodiments described herein.

In 304, a first metal layer may be electroplated onto the fabric, forexample onto one or more of the plurality of carbon fibers. The firstmetal layer may contain or consist of chromium or manganese.Electroplating the first metal layer may, for example, be carried out inaccordance with one or more embodiments described herein, for exampleusing pulsed electroplating.

In 306, a second metal layer may be electroplated onto the first metallayer, for example onto the carbon fibers coated with the first metal.The second metal layer may contain or consist of nickel. Electroplatingthe second metal layer may, for example, be carried out in accordancewith one or more embodiments described herein, for example using pulsedelectroplating.

In 308, the fabric, the first metal layer and the second metal layer maybe annealed. Annealing may, for example, be carried out in accordancewith one or more embodiments described herein.

In 310, a copper layer may be electroplated onto the second metal layer.Electroplating the copper layer may be carried out after annealing thefabric and the first and second metal layers. Electroplating the copperlayer may be effected using any suitable electroplating technique, whichare known as such in the art.

In accordance with another embodiment, a surface of the second metallayer (e.g. a surface that faces away from the first metal layer) may beactivated and/or cleaned before electroplating the copper layer onto thesecond metal layer. Activating the surface of the second metal layer mayinclude the removal of an oxide layer (which may have been formed duringthe annealing) and may, for example, include or be achieved by bringingthe surface into contact with an acid such as hydrochloric acid, e.g.concentrated hydrochloric acid, or other suitable acids. Cleaning thesurface may be carried out after activating the surface and may, forexample, include or be achieved by purging.

In accordance with another embodiment, voids possibly remaining betweenthe plurality of carbon fibers after electroplating the copper layer maybe filled or joined with copper, for example galvanically or by means ofhot pressing.

FIG. 4 shows a method 400 for fabricating a carbon copper composite inaccordance with another embodiment.

In 402, a fabric having a plurality of carbon fibers may be provided.The fabric and/or carbon fibers may, for example, be configured inaccordance with one or more embodiments described herein.

In 404, the carbon fibers may be electroplated with a metal to formmetal-coated carbon fibers. Electroplating may, for example, be carriedout in accordance with one or more embodiments described herein. Themetal may be selected from a group of metals that form a common phasewith both carbon and copper. The metal may, for example, be selected inaccordance with one or more embodiments described herein.

In 406, the fabric having the metal-coated carbon fibers may beannealed. Annealing may, for example, be carried out in accordance withone or more embodiments described herein.

In 408, the metal-coated carbon fibers may be electroplated with copper.Electroplating the copper may be effected using any suitableelectroplating technique, which are known as such in the art. Inaccordance with some embodiments, the metal-coated carbon fibers may beelectroplated with nickel before electroplating copper.

FIG. 5 shows a method 500 for fabricating a carbon copper composite inaccordance with another embodiment.

In 502, a fabric having a plurality of carbon fibers may be provided.The fabric and/or carbon fibers may, for example, be configured inaccordance with one or more embodiments described herein.

In 504, the carbon fibers may be electroplated with a layer stackincluding a first metal layer and a second metal layer disposed over thefirst metal layer to form metal-coated carbon fibers. Electroplatingmay, for example, be carried out in accordance with one or moreembodiments described herein. The first metal layer may contain or maybe made of a first metal and the second metal layer may contain or maybe made of a second metal. The first metal and the second metal may beselected such that the first metal and carbon form at least one commonphase, and the first metal and the second metal form at least one commonphase. The first metal and/or second metal may, for example, be selectedin acordance with one or more embodiments described herein. For example,in accordance with an embodiment, the first metal may be chromium ormanganese. For example, in accordance with another embodiment, thesecond metal may be nickel.

In 506, the fabric having the metal-coated carbon fibers may beannealed. Annealing may, for example, be carried out in accordance withone or more embodiments described herein.

In 508, the metal-coated carbon fibers may be electroplated with copper.Electroplating the copper layer may be effected using any suitableelectroplating technique, which are known as such in the art.

FIG. 6 shows a method for fabricating a carbon copper composite inaccordance with another embodiment.

In 602, a carbon fiber fabric may be provided. The carbon fiber fabricmay, for example, have or be made of a plurality of carbon fibers. Thefabric and/or carbon fibers may, for example, be configurd in accordancewith one or more embodiments described herein.

In 604, a first metal layer may be electroplated over the carbon fiberfabric. Electroplating may, for example, be carried out in accordancewith one or more embodiments described herein. The first metal layer maycontain or consist of a metal that forms a common phase with carbon. Themetal may, for example, be selected in accordance with one or moreembodiments described herein. For example, in accordance with anembodiment, the metal may be chromium or manganese.

In 606, a second metal layer may be electroplated over the first metallayer. Electroplating may, for example, be carried out in accordancewith one or more embodiments described herein. The second metal layermay contain or consist of a metal that forms a common phase with themetal of the first metal layer. The metal may, for example, be selectedin accordance with one or more embodiments described herein. Forexample, in accordance with an embodiment, the metal may be nickel.

In 608, the carbon fiber fabric, the first metal layer and the secondmetal layer may be annealed. Annealing may, for example, be carried outin accordance with one or more embodiments described herein.

In 610, a copper layer may be electroplated over the second metal layer.Electroplating the copper layer may be effected using any suitableelectroplating technique, which are known as such in the art.

FIG. 7A to FIG. 10B illustrate various process stages in a method forfabricating a carbon copper composite in accordance with anotherembodiment.

FIG. 7A and FIG. 7B show, in a plan view 700 and a cross-sectional view750 (corresponding to a cross-section along line 7B-7B′ in FIG. 7A),that a plurality of carbon fibers 702 may be provided. The number ofcarbon fibers 702 may be arbitrary, in general. The carbon fibers 702may, for example, be arranged in bundles 712, wherein each bundle 712may have one or a plurality of carbon fibers 702, as shown. The numberof carbon fibers 702 per bundle 712 may be arbitrary, in general, andmay be the same for each bundle 712 or may be different for differentbundles 712.

The carbon fibers 702, or the bundles 712 of carbon fibers 702, may bearranged to form a fabric 701, as shown. In other words, a layer ofcarbon fibers 702 configured as a carbon fiber fabric 701 may beprovided in accordance with some embodiments. In accordance with otherembodiments, the carbon fibers 702 may be arranged differently. Inaccordance with one or more embodiments, one or more (e.g. all) of thecarbon fibers 702 may include graphite.

At least one (for example a plurality, e.g. all) of the carbon fibers702 may, for example, have a length in the millimeter range, for examplea few millimeters. Other, e.g. higher, values may be possible as well inaccordance with other embodiments.

At least one (for example a plurality, e.g. all) of the carbon fibers702 may, for example, have a diameter in the range from about 1 μm toabout 50 μm. Other values may be possible as well in accordance withother embodiments.

FIG. 8A and FIG. 8B show, in a plan view 800 and a cross-sectional view850 (corresponding to a cross-section along line 8B-8B′ in FIG. 8A),that a first metal layer 703 may be electroplated over the carbon fiberfabric 701. Before depositing the first metal layer 703, the carbonfiber fabric 701 may optionally be pre-cleaned and/or degreased.

The first metal layer 703 may contain or consist of a metal, which formsa common phase with carbon, and a common phase with nickel to bedeposited later (see FIG. 9A and FIG. 9B).

The first metal layer 703 may at least partially (e.g. fully) coat atleast one (for example a plurality, e.g. all) of the carbon fibers 702,as shown.

Electroplating the first metal layer 703 may, for example, be achievedby pulsed electroplating.

A pulse frequency of pulses used in the pulsed electroplating may, forexample, be in the range from about 10 kHz to about 1 MHz. Other valuesmay be possible as well in accordance with other embodiments.

In accordance with another embodiment, a pulse height of pulses used inthe pulsed electroplating may be in the range from about 4 V to about 12V. Other values may be possible as well in accordance with otherembodiments.

In accordance with other embodiments, electroplating the first metallayer may be effected by means of other suitable electroplatingtechniques.

The first metal layer 703 may be deposited such that it has a layerthickness that is smaller than the diameter of the carbon fibers 702,for example substantially smaller than the diameter of the carbon fibers702, for example a layer thickness equal to or less than about 25% ofthe carbon fiber diameter, for example a layer thickness equal to orless than about 15% of the carbon fiber diameter, for example a layerthickness equal to or less than about 10% of the carbon fiber diameter,for example a layer thickness equal to or less than about 5% of thecarbon fiber diameter, for example a layer thickness equal to or lessthan about 1% of the carbon fiber diameter, for example a layerthickness in the range from about 10 nm to about 500 nm. Other valuesmay be possible as well in accordance with other embodiments. Theminimal layer thickness may, for example, correspond to the size ofcrystallization seeds of the first metal layer 703.

FIG. 9A and FIG. 9B show, in a plan view 900 and a cross-sectional view950 (corresponding to a cross-section along line 9B-9B′ in FIG. 9A),that a second metal layer 704 may be electroplated over the first metallayer 703.

The second metal layer 704 may contain or consist of nickel. The nickelof the second metal layer may form a common phase with the first of thefirst metal layer 703, as mentioned above.

The second metal layer 704 may at least partially (e.g. fully) coat atleast one (for example a plurality, e.g. all) of the carbon fibers 702coated with the first metal layer 703, as shown.

Electroplating the second metal layer 704 may, for example, be achievedby pulsed electroplating.

A pulse frequency of pulses used in the pulsed electroplating may, forexample, be in the range from about 10 kHz to about 1 MHz. Other valuesmay be possible as well in accordance with other embodiments.

In accordance with another embodiment, a pulse height of pulses used inthe pulsed electroplating may be in the range from about 4 V to about 12V. Other values may be possible as well in accordance with otherembodiments.

In accordance with other embodiments, electroplating the second metallayer 704 may be effected by means of other suitable electroplatingtechniques.

The second metal layer 704 may be deposited such that it has a layerthickness that is smaller than the diameter of the carbon fibers 702,for example substantially smaller than the diameter of the carbon fibers702, for example a layer thickness equal to or less than about 25% ofthe carbon fiber diameter, for example a layer thickness equal to orless than about 15% of the carbon fiber diameter, for example a layerthickness equal to or less than about 10% of the carbon fiber diameter,for example a layer thickness equal to or less than about 5% of thecarbon fiber diameter, for example a layer thickness equal to or lessthan about 1% of the carbon fiber diameter, for example a layerthickness in the range from about 10 nm to about 500 nm. Other valuesmay be possible as well in accordance with other embodiments. Theminimal layer thickness may, for example, correspond to the size ofcrystallization seeds of the second metal layer 704.

The first metal layer 703 and the second metal layer 704 may, forexample, have the same or substantially the same layer thickness.Alternatively, the layer thicknesses may be different.

The metal of the first metal layer 703 may be selected such that themetal of the first metal layer 703 is a metal which (for example,according to the corresponding phase diagrams) forms at least one commonphase with carbon and at least one common phase with nickel, for examplevia solid state diffusion (in other words, movement and/or transport ofatoms in solid phases) induced by annealing.

Examples for the metal of the first metal layer include chromium ormanganese (for the first metal) as may be seen from FIGS. 11 to 14,which show phase diagrams 1100, 1200, 1300, 1400 of the binary systemscarbon-chromium (C—Cr), carbon-manganese (C—Mn), chromium-nickel(Cr—Ni), and manganese-nickel (Mn—Ni), respectively.

Specifically, as may be seen from the phase diagram 1100 in FIG. 11,carbon (C) and chromium (Cr) may form at least one common phase.

Furthermore, as may be seen from the phase diagram 1200 in FIG. 12,carbon (C) and manganese (Mn) may form at least one common phase.

Furthermore, as may be seen from the phase diagram 1300 in FIG. 13,chromium (Cr) and nickel (Ni) may form at least one common phase.

Furthermore, as may be seen from the phase diagram 1400 in FIG. 14,manganese (Mn) and nickel (Ni) may form at least one common phase.

Furthermore, nickel may adhere well to copper.

Alternatively, other combinations of metals may be possible for thefirst and second metal layers 703, 704.

Illustratively, the first metal layer 703 and the second metal layer 704may serve as adhesion layers to enable or improve adhesion of a copperlayer 705 to be deposited later (see FIG. 10A and FIG. 10B).

The carbon fiber fabric 701 (including the carbon fibers 702), the firstmetal layer 703 and the second metal layer 704 may be annealed to formthe common phases.

The fabric 701 and the metal layers 703, 704 may, for example, beannealed to a temperature in the range from about 400° C. to about 1000°C. Other values may be possible as well in accordance with otherembodiments.

The fabric 701 and the metal layers 703, 704 may, for example, beannealed for a time duration in the range from about 1 h to about 10 h.Other values may be possible as well in accordance with otherembodiments.

The fabric 701, the first metal layer 703 and the second metal layer 704may be annealed simultaneously after deposition of the second metallayer 704 to form the common phases. In other words, a single annealingstep may be carried out to anneal the fabric 701 and the metal layers703, 704. However, it may also be possible to carry out a firstannealing step before deposition of the second metal layer 704, and asecond annealing step after deposition of the second metal layer 704 toanneal the fabric 701 and the metal layers 703, 704.

Annealing the fabric 701, the first metal layer 703 and the second metallayer 704 may serve to form a common phase of carbon (of the carbonfibers 702) and the metal of the first metal layer 703 (e.g. chromium ormanganese), for example at an interface between the carbon fibers 702and the first metal layer 703, and a common phase of the metal of thefirst metal layer 703 (e.g. chromium or manganese) and the metal of thesecond metal layer 704, for example at an interface between the firstmetal layer 703 and the second metal layer 704.

In accordance with another embodiment, a surface of the second metallayer 704 that faces away from the first metal layer 703(illustratively, an outer surface of the second metal layer 704) mayoptionally be activated, for example in concentrated hydrochloric acid(e.g. for a short time interval of about 10 s to about 20 s), and/orcleaned (e.g. purged) after annealing the second metal layer 704.

FIG. 10A and FIG. 10B show, in a plan view 1000 and a cross-sectionalview 1050 (corresponding to a cross-section along line 10B-10B′ in FIG.10A), that a copper layer 705 may be electroplated over the second metallayer 704. Electroplating the copper layer 705 may be effected using anysuitable electroplating technique, which are known as such in the art.

In accordance with another embodiment, voids possibly remaining betweenthe plurality of metal-coated carbon fibers 702 after electroplating thecopper layer 705 may be filled or joined with copper, for examplegalvanically or by means of hot pressing.

FIG. 10A and FIG. 10B illustratively show a carbon copper composite inaccordance with an embodiment.

The carbon copper composite may include a plurality of carbon fibers702. The carbon fibers 702 may, for example, be arranged to form afabric 701, also referred to as carbon fiber fabric.

The carbon copper composite may further include a first metal layer 703.The first metal layer may 703 be disposed over the carbon fibers 702.The first metal layer 703 may contain or consist of a metal that forms acommon phase with carbon and a common phase with nickel.

The carbon copper composite may further include a second metal layer704. The second metal layer 704 may be disposed over the first metallayer 703. The second metal layer 704 may contain or consist of nickel.The metal of the first metal layer 703 may, for example, be chromium ormanganese. Alternatively, any other combination of metals, which maymeet the aforementioned conditions, may be used.

The carbon copper composite may further include a copper layer 705. Thecopper layer 705 may be disposed over the second metal layer 704.

Illustratively, FIG. 10A and FIG. 10B show a carbon copper compositethat includes an adhesion layer stack 703/704 disposed between a layerof carbon fibers 702 and a copper layer 705, the layer stack 703/704including two adhesion layers (in other words, layers establishing orimproving adhesion between carbon and copper) disposed one over theother, i.e. the first metal layer 703 and the second metal layer 704.

In accordance with some embodiments, a carbon copper composite mayinclude only one metal layer as adhesion layer disposed between thecarbon fibers 702 and the copper layer 705. In this case, the metallayer may contain or consist of a metal that may form a common phasewith carbon and a common phase with copper, for example chromium ormanganese.

Carbon copper composites as described herein may, for example, be usedas a heat sink for an electronic device such as, for example, a powerelectronic device or component (e.g. a high power module). To this end,the carbon copper composite may be attached to the electronic device,for example to a substrate of the electronic device.

In the following, various aspects and potential effects of variousembodiments are described.

In accordance with various embodiments, one or more carbon fibers may beelectrolytically coated with a metal that forms at least one commonphase with carbon and at least one common phase with copper (accordingto the corresponding phase diagrams), and subsequently annealed to forma carbon-metal phase at the carbon-metal interface. The metal layer mayillustratively serve as bonding agent or adhesion layer for a copperlayer do be deposited later (in other words, as a layer that may enableor improve adhesion of the copper layer).

In accordance with various embodiments, one or more carbon fibers may beelectrolytically coated with a metal layer stack including a first metal(e.g. chromium or manganese) that forms at least one common phase withcarbon and a second metal (e.g. nickel) that forms at least one commonphase with the first metal, and subsequently annealed to form acarbon-metal phase at the interface between the carbon fiber(s) and thefirst metal, and a metal-metal phase at the interface between the firstmetal and the second metal. The metal layer stack may illustrativelyserve as adhesion layer stack for a copper layer to be coupled to thecarbon fibers (in other words, as a layer stack that may enable orimprove adhesion of the copper layer on the carbon fibers).

In accordance with various embodiments, at least one metal layer may beelectroplated onto one or more carbon fibers (e.g. a carbon fiberfabric) to serve as an adhesion layer or bonding agent to improveadhesion of a copper layer to be plated onto the fibers. The at leastone metal layer may contain or consist of at least one metal (e.g.chromium or manganese) that forms at least one common phase with bothcarbon and copper.

In accordance with various embodiments, a copper layer may beelectroplated onto the metal-coated carbon fiber(s), i.e. onto thecarbon fiber(s) coated with the adhesion layer(s), thereby forming acarbon copper composite. The carbon copper composite may, for example,be used as heat sink material.

Thus, in accordance with various embodiments, a heat sink material orheat sink may be provided, e.g. for a power electronic device or powerelectronic component such as e.g. a high power module (e.g. IGBT(insulated gate bipolar transistor) module)), based on a carbon coppercomposite.

The carbon copper composite including the carbon fibers and copper mayhave a coefficient of thermal expansion (CTE), which is much closer tothe CTE of silicon than the CTE of pure copper. Therefore, the carboncopper composite may greatly reduce thermal stress and chip bending whenused as heat sink material.

One aspect of various embodiments may be seen in that carbon fibers maybe provided with a surface that enables cold fabrication of a carboncopper composite directly at a wafer.

Another aspect of various embodiments may be seen in that methods areprovided, by means of which a composite of carbon fibers and copper(CCu) may be adapted to become suitable for many temperature cycles.

Another aspect of various embodiments may be seen in that one or more ofthe drawbacks of the above-described conventional method for fabricatinga CCu composite may be obviated or substantially reduced.

For example, a sintering process as in the conventional method may notbe needed to fabricate a CCu composite. Thus, a cold fabrication of aCCu composite directly at a wafer becomes possible. Furthermore, noadditives may be needed in the copper electrolyte to improve adhesion ofthe copper.

Another aspect of various embodiments may be seen in that a CCucomposite may be provided that may be suitable for thermal cycling, forexample a CCu composite that may resist many temperature cycles with noor substantially no degradation.

According to various embodiments, at least one bonding agent is providedon the carbon fibers. The bonding agent may be realized by a galvaniccoating of a metal, which forms at least one common phase with carbon,and with the later-deposited copper.

Examples of metals, which may be deposited relatively easily by means ofaqueous electrolysis, include, for example, chromium and manganese.

According to some embodiments, a layer of nickel may be deposited asadditional (second) intermediate layer after deposition of a first metallayer (chromium or manganese layer), which forms a common phase withboth chromium and manganese.

According to various embodiments, the common phase between carbon andthe first metal may be formed by means of a temperature treatment(annealing).

According to some embodiments, the annealing may be carried out in thepresence of the second metal (nickel).

According to some embodiments, an oxide layer, which may possibly begenerated on the surface of the second metal layer (nickel layer) duringthe annealing, may be removed, for example by bringing the oxidizedmetal layer into contact with an acid such as concentrated hydrochloricacid, thereby activating the surface for a subsequent electrolyticcopper plating.

According to some embodiments, carbon fibers may be provided with adouble pre-coating, including a first galvanically deposited metal layer(e.g. chromium or manganese layer) and a second galvanically depositedmetal layer (nickel layer) deposited over the first metal layer.

According to some embodiments, the deposition of the metal layer orlayers onto the carbon fibers may be carried out using a galvanic pulsedeposition. By means of a galvanic pulse deposition, a very thin and/orhomogeneous coating may be achieve, since crystallization seeds maybecome smaller with increasing difference in the chemical potentialbetween the starting species of the metal to be deposited (i.e. theelectrolytic solution) and the final state (i.e. the metallic film). Forexample, layer thicknesses down to approximately the seed size may beachieved by means of galvanic pulse deposition.

FIG. 15A and FIG. 15B show two electron micrographs illustrating seedformation in galvanic pulse deposition of nickel on silicon, whereinFIG. 15B is a magnification of a part of FIG. 15A. The micrographs serveas an example to illustrate how pulse height and/or pulse width of apulse galvanic may influence size, density and/or layer thickness ofseeds of a metallic coating. The figures show that very thin layerthicknesses may be achieved with galvanic pulse deposition.

Reducing the thickness of the metal coating (i.e. of the adhesion layeror layers) may improve the thermal and/or electrical conductivity of thecarbon copper composite.

In accordance with some embodiments, an adhesion layer stack may beprovided for a cold electrolytic fabrication of a carbon fiber-coppercomposite material, wherein a first metal, e.g. chromium or manganese(or any other material that forms a common phase with both carbon andnickel), is deposited onto a (e.g. pre-cleaned and degreased) carbonfiber fabric by means of electrolytic deposition (e.g. galvanic pulsedeposition) in aqueous solution, and wherein subsequently nickel isdeposited onto the first metal (also by electrolytic deposition, e.g.galvanic pulse deposition). The adhesion metals may be substantiallythinner than the diameter of the carbon fibers. Subsequently, the carbonfiber fabric provided with the metallic adhesion layer stack may beannealed (in other words, heated or tempered). Subsequently, the nickelsurface may be activated for a short time interval in concentratedhydrochloric acid and purged. Subsequently, copper may be deposited bymeans of electrolytic deposition. Possibly remaining voids may beconnected with copper, e.g. galvanically and/or by means of hotpressing.

A method for fabricating a carbon copper composite in accordance withanother embodiment may include: providing a first layer, the first layerhaving or being made of a plurality of carbon fibers; electroplating ametal layer over the first layer, the metal layer containing orconsisting of a metal that forms a common phase with carbon and a commonphase with copper; annealing at least the first layer and the metallayer; electroplating a second layer over the metal layer, the secondlayer containing or consisting of copper.

A method for fabricating a carbon copper composite in accordance withanother embodiment may include: providing a first layer, the first layerhaving or being made of a plurality of carbon fibers; electroplating afirst metal layer over the first layer, the first metal layer containingor consisting of a first metal, and electroplating a second metal layerover the first metal layer, the second metal layer containing orconsisting of a second metal, wherein the first metal and the secondmetal are selected such that the first metal and carbon form a commonphase and the first metal and the second metal form a common phase;annealing the first layer, the first metal layer and the second metallayer; electroplating a second layer over the second metal layer, thesecond layer containing or consisting of copper.

A method for fabricating a carbon copper composite in accordance withanother embodiment may include: providing a fabric having a plurality ofcarbon fibers; electroplating at least one metal layer over the fabric,the at least one metal layer containing or consisting of a metal thatforms at least one common phase with carbon and at least one commonphase with copper; annealing the fabric and the at least one metallayer; electroplating a copper layer over the at least one metal layer.

A carbon copper composite in accordance with another embodiment mayinclude: a first layer, the first layer containing or consisting of aplurality of carbon fibers; a metal layer disposed over the first layer,the metal layer containing or consisting of a metal that forms a commonphase with carbon and a common phase with copper; a second layerdisposed over the metal layer, the second layer containing or consistingof copper.

In accordance with various embodiments, a method for fabricating acarbon copper composite may include: providing a carbon fiber fabric;electroplating a first metal layer over the carbon fiber fabric, thefirst metal layer containing or consisting of a metal that forms acommon phase with carbon (e.g. chromium or manganese); electroplating asecond metal layer over the first metal layer, the second metal layercontaining or consisting of nickel; annealing the carbon fiber fabric,the first metal layer and the second metal layer; electroplating acopper layer over the second metal layer.

In accordance with various embodiments, a method for fabricating acarbon copper composite may include: providing a fabric having aplurality of carbon fibers; electroplating the carbon fibers with atleast one metal to form metal-coated carbon fibers, the at least onemetal being selected from a group of metals that form at least onecommon phase with carbon and at least one common phase with copper;annealing the fabric having the metal-coated carbon fibers;electroplating the metal-coated carbon fibers with copper.

In accordance with various embodiments, a method for fabricating acarbon copper composite may include: providing a fabric having aplurality of carbon fibers; electroplating the carbon fibers with alayer stack including a first metal layer and a second metal layerdisposed over the first metal layer to form metal-coated carbon fibers,the first metal layer containing or being made of a first metal and thesecond metal layer containing or being made of a second metal, whereinthe first metal and the second metal are selected such that the firstmetal forms a common phase with carbon and a common phase with thesecond metal; annealing the fabric having the metal-coated carbonfibers; electroplating the metal-coated carbon fibers with copper.

While the invention has been particularly shown and described withreference to specific embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. The scope of the invention is thusindicated by the appended claims and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced.

What is claimed is:
 1. A method for processing at least one carbonfiber, comprising: electroplating a first metal layer over at least onecarbon fiber, wherein the first metal layer comprises a metal which canform a common phase with carbon; electroplating a second metal layerover the first metal layer, wherein the second metal layer comprises ametal which can form a common phase with the metal of the first metallayer; and annealing the at least one carbon fiber, the first metallayer, and the second metal layer so that the metal of the first metallayer forms a common phase with the carbon of the at least one carbonfiber at an interface between the first metal layer and the at least onecarbon fiber and the metal of the first metal layer forms a common phasewith the metal of the second metal layer at an interface between thefirst metal layer and the second metal layer.
 2. The method of claim 1,wherein the metal of the first metal layer is chromium or manganese andthe metal of the second metal layer is nickel.
 3. The method of claim 2,wherein the annealing is performed at a temperature in the range fromabout 400° C. to about 1000° C.
 4. The method of claim 2, wherein theannealing is performed for a time duration in the range from about 1hour to about 10 hours.
 5. The method of claim 1, wherein the annealingof the at least one carbon fiber, the first metal layer, and the secondmetal layer is performed simultaneously.
 6. The method of claim 1,wherein at least one of the thickness of the first metal layer and thethickness of the second metal layer is approximately the size ofcrystallization seeds of the respective metal layer.
 7. The method ofclaim 1, wherein the at least one carbon fiber comprises graphite andwherein the diameter of the at least one carbon fiber is in the rangefrom about 1 μm to about 50 μm.
 8. The method of claim 1, wherein atleast one of electroplating the first metal layer and electroplatingsecond metal layer comprises pulsed electroplating.
 9. The method ofclaim 1, further comprising: at least one of activating and cleaning asurface of the second metal layer after annealing the second metallayer.
 10. The method of claim 1, further comprising: electroplating acopper layer over the second metal layer.
 11. The method of claim 10,further comprising: annealing the copper layer at a temperature in therange from about 110° C. to about 150° C.
 12. A method for fabricating acarbon copper composite, comprising: providing a plurality of carbonfibers; electroplating a first metal layer over the plurality of carbonfibers, wherein the first metal layer comprises a metal which can form acommon phase with carbon; electroplating a second metal layer over thefirst metal layer, wherein the second metal layer comprises a metalwhich can form a common phase with the metal of the first metal layer;annealing the plurality of carbon fibers, the first metal layer, and thesecond metal layer so that the metal of the first metal layer forms acommon phase with the carbon of the plurality of carbon fibers at aninterface between the first metal layer and the plurality of carbonfibers and the metal of the first metal layer forms a common phase withthe metal of the second metal layer at an interface between the firstmetal layer and the second metal layer; and electroplating a copperlayer over the second metal layer.
 13. The method of claim 12, whereinthe metal of the first metal layer is chromium or manganese and themetal of the second metal layer is nickel.
 14. The method of claim 12,wherein wherein at least one of electroplating the first metal layer andelectroplating the second metal layer comprises pulsed electroplating.15. The method of claim 12, further comprising: at least one ofactivating and cleaning a surface of the second metal layer beforeelectroplating the copper layer over the second metal layer.
 16. Themethod of claim 12, wherein the plurality of carbon fibers comprises afabric.
 17. The method of claim 12, further comprising: filling voidsbetween the plurality of copper coated carbon fibers with copper.
 18. Amethod for fabricating a carbon copper composite heatsink, the methodcomprising: providing a carbon fiber fabric; electroplating a firstmetal layer onto the carbon fiber fabric, the first metal layercomprising chromium or manganese; electroplating a second metal layeronto the first metal layer, the second metal layer comprising nickel;annealing the carbon fiber fabric, the first metal layer, and the secondmetal layer so that the chromium or manganese of the first metal layerforms a common phase with the carbon of the carbon fiber fabric at aninterface between the first metal layer and the carbon fiber fabric andthe chromium or manganese of the first metal layer forms a common phasewith the nickel of the second metal layer at an interface between thefirst metal layer and the second metal layer; and electroplating acopper layer onto the second metal layer.
 19. The method of claim 18,wherein electroplating of at least one of the first and second metallayers comprises pulsed electroplating.
 20. The method of claim 18,further comprising: pre-cleaning and degreasing the carbon fiber fabricbefore electroplating the first metal layer onto the carbon fiberfabric; and at least one of activating and cleaning a surface of thesecond metal layer before electroplating the copper layer over thesecond metal layer.